Camera-assisted adjustment of bonding head elements

ABSTRACT

The invention relates to a method which is used to carry out adjusting operations on a bond head, wherein a bond head element is positioned in relation to a reference element, especially an ultrasonic tool. According to the invention, at least the surrounding area of the reference element, especially the tip of the ultrasonic tool, is optically detected by means of a camera and is displayed in an image on a display device. A marking is superimposed in the display in order to facilitate positioning. The invention also relates to an ultrasonic bonder comprising a camera which is used to support the positioning of a bond head element. Said camera can optically detect at least the area surrounding the reference element, especially the tip of the ultrasonic tool.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/EP2004/008018 filed on Jul. 17, 2004, which designates theUnited States and claims priority of German Patent Application No.10338809.5 filed on Aug. 21, 2003.

FIELD OF THE INVENTION

The invention relates to a method and an apparatus for carrying outsetting operations on a bonding head, in which a bonding head element ispositioned relative to a reference element, such as for example anultrasonic tool, in particular its tip.

BACKGROUND OF THE INVENTION

In the context of ultrasonic bonders which have a bonding head with anultrasonic tool attached to it, for example for carrying out wirebonding, it is known that various bonding head elements have to bepositioned relative to the ultrasonic tool and in particular relative toits tip.

By way of example, accurate positioning of a wire feed relative to thetip of the ultrasonic tool is required to ensure that the wire which issupplied is always located precisely beneath the tip of the ultrasonictool, for example in a V-shaped groove. Accurate positioning of the wirefeed relative to the tip of the ultrasonic tool is necessary to enablethe production of wire bonds of perfect quality.

Also, if a separate blade is used to sever the bonding wire or toproduce a desired breaking point, it is also necessary for such a bladeto be accurately positioned relative to the ultrasonic tool.

It is known for positioning operations of this type to be performedmanually by the user of an ultrasonic bonder. Experience has shown thatthis is subject to considerable inaccuracies, since the operating useris reliant upon his own senses to achieve sufficiently accuratepositioning of these elements with respect to one another. However, inmany cases manual positioning cannot be considered adequate, andconsequently the quality of bonds can then leave something to be desiredand/or specifically defective bonds may be produced.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a method and/or anultrasonic bonder by which accurate positioning of a bonding headelement relative to a reference element, such as for example theultrasonic tool, is made possible.

According to the method of the invention, this object is achieved byvirtue of the fact that at least a region surrounding the referenceelement, in particular the tip of the ultrasonic tool, is opticallycaptured by means of a camera and is displayed in an image on a displaydevice, at least one marking being overlaid into the display as anauxiliary means for positioning bonding head elements.

A method according to the invention of this nature can be carried out,for example, by means of an ultrasonic bonder, which to assist withpositioning of a bonding head element has a camera, by means of which atleast a region around the reference element, e.g. the tip of theultrasonic tool, can be optically captured. A camera of this type may beprovided directly on the ultrasonic bonder or may form a separatedevice, so that even existing ultrasonic bonders can be retrofitted soas to carry out the method according to the invention.

The optical capture of at least a region around the reference element,such as, for example the tip of the ultrasonic tool, gives an enlargedimage, which is displayed in particular on a display device, for exampleof the tip of the ultrasonic tool and the further bonding head elementsdisposed around it, such as for example a wire feed and/or a blade orother elements that are to be adjusted.

The capture and display of the corresponding image of the region aroundthe reference element, in particular the tip of an ultrasonic tool, anda marking as auxiliary assistance relieves the work of an operator, whono longer has to rely on his own senses in observing the ultrasonictool. In particular, a preferred enlarged representation achievesincreased accuracy when positioning the elements with respect to oneanother, for which purpose according to the invention it is providedthat a desired position, and therefore an optimum position of a bondinghead element relative to the reference element, for example theultrasonic tool, is represented by a marking in the image, which anoperator can use for orientation purposes.

A bonding head element can be set in such a manner that it appears inthe image in the desired position relative to the reference element, forexample by virtue of the fact that an adjustment point on a bonding headelement is brought into line with the marking. It is also possible toprovide for the marking to reproduce the contour of the bonding headelement that is to be adjusted and for the bonding head element to bepositioned into this contour.

It is preferably also possible to provide for a marking to be presentedin the form of a tolerance field in the image relative to the referenceelement, in particular relative to the tip of the ultrasonic tool.Displaying a tolerance field provides the user with access to a regioninto which the bonding head element that is to be set is to bepositioned. By way of example, it is then possible for a distinctivelocation on the bonding head element, e.g. its tip, to be positionedinto this tolerance field. In this case, a tolerance field may beprovided, for example, within the image in the form of a rectangularrepresentation of parallel lines, or if appropriate just by two parallellines, or if there are no tolerances, by a cross.

Particular accuracy in terms of the positioning can be effected from thelocation, in the image, of a tolerance field or any marking whichrepresents a desired position of a bonding head element being determinedby a data processing unit as a function of the location of the referenceelement or a reference point, in particular the tip of the ultrasonictool in the image.

Therefore, the position of the adjustment marking, e.g. the tolerancefield, can be determined on a computer-aided basis using internalcriteria of the ultrasonic bonder, so that all the operator has to do isto position the bonding head element that is to be positioned withrespect to the marking by operating suitable adjustment means.

To allow an adjustment marking e.g. of the tolerance field to bepresented as a function of the location of the reference element, suchas for example the tip of the ultrasonic tool, in an alternative it ispossible to provide for the location of the reference element to bedetermined manually, in particular by marking this location in theimage. To effect this, it is possible, for example, to provide for anoperator to mark the corresponding location of a reference element, i.e.a reference point, in the image presented on the display device, forexample by clicking on the tip or an edge of the tip of the ultrasonictool by means of a mouse pointer. A marking can also be produced bytouching a touchscreen of the display device or by other suitablemeasures for communicating the location of the reference element to thedata processing unit.

This marking can be used, for example, to capture the precise positionof the tip of the ultrasonic tool by computer means in order then todetermine the optimum position for the adjustment marking, e.g. thetolerance field, as a function of this position and to present it in theimage on the display device.

According to a further alternative, it is also possible to provide forthe location of the reference element, e.g. the tip of the ultrasonictool, to be determined by computer-aided image recognition. For example,a computer program can be used to carry out pattern recognition in orderto recognize the reference element, such as the tip of the ultrasonictool, in the image captured and to determine the position. Then, basedon this automatically computer-aided position recognition, it ispossible to calculate the optimum position of the adjustment marking,e.g. the tolerance field in the image, in order for this position thento be incorporated into the image.

The positioning of any bonding head element, such as for example a wireguide or a blade, preferably has to be implemented optimally or withinacceptable tolerances in all three dimensions. If at least the regionaround the tip of an ultrasonic tool is captured, in each case only atwo-dimensional image can ever be formed, and consequently in each caseonly two-dimensional optimum positioning of the elements with respect toone another can be achieved in any one adjustment step.

To allow optimum positioning of a bonding head element relative to thereference element, such as the ultrasonic tool, at least initially intwo dimensions, according to the invention it is possible to providethat the camera records at least one side view onto the referenceelement, therefore for example at least onto the tip of the ultrasonictool, and/or a view onto the reference element perpendicularly withrespect thereto, such as for example onto the end face of the tip of theultrasonic tool. In particular when both options have been completed,the result is two different views from directions that are perpendicularto one another, so that ultimately a bonding head element can bepositioned optimally with respect to all three dimensions.

To allow the view onto the reference element, e.g. onto the tip of theultrasonic tool, in the different directions, it is preferably possibleto provide that to change between the views a mirror is positioned inthe beam path between the camera and the reference element. This mirroris preferably set up in such a manner that the beam path between thecamera and the reference element, such as the tip of the ultrasonictool, is diverted by 90° when the mirror is used.

In this case, to change from the lateral view of the reference element,in which for example the tip of the ultrasonic tool is locatedpreferably precisely at the height of the optical axis of the camera, toa view onto the reference element, e.g. onto the end face, it ispossible for the bonding head and therefore the reference element to bedisplaced in the Z direction and preferably at the same time parallel tothe optical axis of the camera relative to the latter, in particular insuch a way that the length of the beam path remains constant.

Therefore, when considering the overall installation, in which thebonding head is located above the camera following this displacement, amirror can be moved at a 45 degree orientation under the referenceelement, e.g. under the tip of the ultrasonic tool, in order thereby forthe beam path to be correspondingly diverted and to allow an undisturbedview for example onto the end face and in particular the groove of theultrasonic tool.

With the method according to the invention and the ultrasonic bonderaccording to the invention, there is preferably provision for both awire guide and a blade to be positioned relative to the tip of anultrasonic tool. In principle, however, it is possible for anyconceivable element on a bonding head to be positioned relative to anydesired reference element or any desired reference point.

Since the light conditions in the region around the bonding headelements to be observed may be inadequate, it is possible toadditionally provide, in a refinement, that the bonding head elementsthat are to be adjusted are artificially illuminated in order for theimage to be captured. In particular, light-emitting diodes, which arepreferably disposed around the camera objective, can be used for thispurpose.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is illustrated in the drawingsbelow, in which:

FIG. 1 shows part of an ultrasonic bonder with a bonding head providedon it and a camera for visual observation of the tip of the ultrasonictool;

FIG. 2 presents a lateral image, captured by the camera, of the tip ofthe ultrasonic tool and its vicinity together with further bonding headelements;

FIG. 3 shows a camera arrangement relative to the tip of the ultrasonictool using a mirror to divert the beam path;

FIG. 4 shows an image, captured by the camera, of the tip of anultrasonic tool and its vicinity in the form of a view onto the end faceof the tip.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a partial excerpt from an ultrasonic bonder with a bondinghead 1 which is disposed thereon and in the usual way includes anultrasonic transducer 2 which is provided on it and to which anultrasonic tool in the form of a wedge 3 is secured. Furthermore, at theultrasonic bonder, a camera 8, which in the illustration shown in FIG. 1records a lateral view of the tip or the region around the tip of theultrasonic tool 3, is provided on a corresponding holder.

FIG. 2 shows a corresponding lateral image which can be viewed by a useron the display device of the camera, for example a screen. The relativearrangement of the wire guide 4 for supplying a wire 12 to the tip 3 bof the ultrasonic tool 3 and of the blade 5 disposed between theseelements with respect to the ultrasonic tool 3 can be clearly seen.

According to the invention, it is possible to provide that a user marksthe front edge 3 b of the tip of the ultrasonic tool, for example usinga mouse pointer, in order to communicate the position of the tip to adata processing unit. According to another embodiment, it is possible toprovide that this position is determined automatically by patternrecognition.

On account of the position of the tip 3 b of the ultrasonic tool 3having been predetermined in this way, the data processing unit is ableto calculate optimum positioning both of the wire guide 4 and also, inthis embodiment, of the blade tip 5 by taking account of internalcriteria. In the present case, this optimum position for the wire guide4 is presented in the form of a corresponding tolerance field 6 withinthe image. The optimum position for the positioning of the blade tip 5is also overlaid into the image by way of a tolerance field 7.

In order then to achieve an optimum position of these elements 4, 5, auser, for example by operating suitable setting mechanisms, can disposethe respective tips of both the wire guide 4 and the blade 5 within thetolerance fields 6, 7 presented, which in this case are substantiallyrectangular in form.

In a further embodiment, it is also possible to provide that the dataprocessing unit effects positioning of the bonding head elementsautomatically by corresponding control of the setting mechanisms. Insuch a case, the relative positioning of these elements can be effectedfully automatically.

The embodiment shown in FIGS. 1 and 2, with a side view, only allows thepositioning of the wire guide 4 and the blade 5 in two dimensions,namely the Y and Z directions based on FIG. 2.

To also achieve optimum positioning with regard to the remainingdimension in the X direction, according to the present embodiment thereis provision for the beam path to be diverted by a mirror 10, which canbe effected for example by introducing a mirror 10 which is tilted at45° on a holding arm 11 into the beam path after the bonding head 1 hasbeen displaced in the Z direction and parallel to the optical axis ofthe camera, so that the diverted beam path now provides the camera witha view onto the end face of the tip of the ultrasonic tool 3.

An arrangement as shown in FIG. 3 therefore results in an imagecorresponding to FIG. 4 in the X-Y plane, in which in addition to theV-shaped groove 3 a in the tip of the ultrasonic tool 3, the respectivetips of the wire guide 4 and the blade 5 can also be recognized. Inparticular, in this case the groove 4 a in the wire guide 4 can berecognized; this groove is used to feed a wire 12 under the V-shapedgroove 3 a in the ultrasonic tool 3.

Optimum positioning is achieved if the course of the groove 4 a of thewire guide 4 is aligned with the V-shaped groove 3 a in the ultrasonictool 3, in order for the wire 12 to be supplied without disruption.

To find this positioning, it is in turn possible to provide for theposition to be determined on the basis of a distinctive location on thetip of the ultrasonic tool, for example at the edge 3 b, either manuallyby the user or by pattern recognition by a computer. As a function ofthis position determination, a marking or a tolerance field 13, in thiscase for example in the form of two parallel lines, can be superimposedon the image, in order thereby to allow optimum positioning of thegroove 4 a of the wire guide 4. This positioning is achieved when theside walls of the groove 4 a are aligned with the lines of the tolerancefield 13 as illustrated in FIG. 4.

Therefore, in particular by diverting the beam path by means of a mirror10, it is possible to achieve optimum positioning of the bonding headelements, for example a wire guide and a blade, relative to the tip ofan ultrasonic tool in all three dimensions.

Should the light conditions prove inadequate, it is possible, asillustrated here, for light-emitting diodes 9 to be disposed around thecamera objective, providing for sufficient illumination in the vicinityof the tip of the ultrasonic tool 3.

1. Method for carrying out setting operations on a bonding head, as partof which setting operations a bonding head element is positionedrelative to a reference element, characterized in that at least a regionsurrounding the reference element is optically captured by means of acamera and is displayed in an image on a display device, a marking beingoverlaid into the display as an auxiliary means for the positioning. 2.Method according to claim 1, characterized in that the bonding headelement is set in such a manner that it appears in the image in adesired position, corresponding to the marking, relative to thereference element.
 3. Method according to claim 2, characterized in thatthe marking is presented in the form of a tolerance field in the imagerelative to the reference element.
 4. Method according to claim 3,characterized in that the location of a tolerance field in the image isdetermined by a data processing unit as a function of the location ofthe reference element in the image.
 5. Method according to claim 1,characterized in that the location of the reference element isdetermined manually.
 6. Method according to claim 1, characterized inthat to position the bonding head element, there is recorded by thecamera at least one view onto the reference element.
 7. Method accordingto claim 5, characterized in that to change between the views, a mirroris positioned in the beam path between camera and reference element. 8.Method according to claim 6, characterized in that to record a view ontothe reference element, the bonding head is displaced in the Z directionand parallel to the optical axis of the camera.
 9. Method according toclaim 1, characterized in that at least one of the bonding head element,a wire guide and a blade is positioned relative to a tip of anultrasonic tool.
 10. Method according to claim 1, characterized in thatthe bonding head elements are artificially illuminated in order tocapture the image.
 11. Ultrasonic bonder having a bonding head, whichhas an ultrasonic tool and at least one positionable bonding headelement, characterized in that the ultrasonic bonder has a camera, bymeans of which at least a region around a reference element can beoptically captured, to assist with positioning of the bonding headelement.
 12. Method according to claim 1, characterized in that thereference element comprises an ultrasonic tool.
 13. Method according toclaim 12, characterized in that the region surrounding the referenceelement comprises a tip of the ultrasonic tool.
 14. Method according toclaim 5, characterized in that the location of the reference element isdetermined manually by marking in the image.
 15. Method according toclaim 5, characterized in that the location of the reference element isdetermined manually by computer-aided image recognition.
 16. Methodaccording to claim 6, characterized in that to position the bonding headelement, there is recorded by the camera at least one side view onto thetip of the ultrasonic tool.
 17. Method according to claim 6,characterized in that to position the bonding head element, there isrecorded by the camera at least view onto an end face of the tip of theultrasonic tool.
 18. Method according to claim 8, characterized in thatthe bonding head is displaced in such a manner that the focus distanceremains constant.
 19. Method according to claim 10, characterized inthat the bonding head elements are artificially illuminated bylight-emitting diodes disposed around a camera objective.
 20. Ultrasonicbonder according to claim 11 characterized in that the reference elementcomprises a tip of the ultrasonic tool.